Tellie saw the entire battle unfold right in front of her eyes and could not believe that her commander was able to get away with such a stunt. He not only defied how things usually work in this world but also go against every single textbook tactic she had ever read.
What's more was that with just a single shot, he was able to find where the enemy was coming from and even with the Mechanoids' processing speed to analyse the situation, most War Maidens were not able to do so. Yet, this supposed outsider who was banished by the 'heavens' was doing things that made the War Maidens feel obsolete.
And to make Tellie feel even worse, he was able to trigger off a sniper rifle while dodging the next shot, giving a direct hit to the shooter. It felt like Jin was somewhat cheating and made Tellie determine that she had to do more than what she usually could.
Diaz: Contact! Contact! Three hostiles hiding in the red building!